In yeast mitochondria, processing RNA includes excision of intervening sequences RNA splicing and excision of terminal sequences. We have previously cataloged over 40 mitochondrial RNA species other than tRNA, and many of these appear to be precursors of fully processed RNA. It is planned to analyze processing relations by hybridizing specific gene probes to RNA species. We will then purify transcripts and analyze their cell-free translation. We will also examine the effects on processing caused by biological manipulation of mitochondria, including anaerobiasis, glucose repression, and oxygen adaptation. We will have localized promoters and processing sites in the genome, we will then define them by DNA and RNA sequencing. Further, we will attempt to characterize and purify the enzyme that carry out excision and splicing of intervening sequences, terminal excision of RNA segments, and tRNA processing. Yeast mitochondria are structurally and functionally the same as animal mitochondria and this study should give considerable information about the way mitochondria are assembled. In addition, the study of RNA processing from genes containing intervening sequences is a general problem in the biology of all higher cells, and the yeast mitochondrion should be a particularly convenient system for study of this problem.